WIDESPREAD EXPRESSION AND ESTROGEN REGULATION OF PPEIA-3' NUCLEAR-RNAIN THE RAT-BRAIN

We previously identified a novel nuclear RNA species derived from the preproenkephalin (PPE) gene. This transcript, which we have named PPEI A-3' RNA, hybridizes with probes directed at a region of PPE intron A downstream of an alternative germ-cell transcription start site, but d oes not contain PPE protein coding sequences. We now report that estro gen treatment of ovariectomized rats increases the expression of conve ntional PPE heteronuclear RNA, and also induces the expression of PPEI A-3' RNA, apparently in separate cell populations within the ventromed ial nucleus of the hypothalamus. Further, we show that cells expressin g PPEIA-3' are found in several neuronal groups in the rat forebrain a nd brainstem, with a distinct topographical distribution. High densiti es of PPEIA3' containing cells are found in the reticular thalamic nuc leus, the basal forebrain, the vestibular complex, the deep cerebellar nuclei, and the trapezoid body, a pattern that parallels the distribu tion of atypical nuclear RNAs described by other groups. These results suggest that this diverse neuronal population shares a common set of nuclear factors responsible for the expression and retention of this a typical RNA transcript. The implication of these results for cell-spec ific gene transcription and regulation in the brain and the possible r elationship of PPEIA-3' RNA and other atypical nuclear RNAs is discuss ed.